An eighteen-year span of global cooling that is recorded in Irish bog oaks has been attributed to H-3.[3][4] The eruption is detectable in Greenland ice-cores, the bristlecone pine sequence, and the Irish oak sequence of extremely narrow growth rings. Andy Baker's team of researchers dated it to 1021 BC ±130–100.[5]

A "high chronology" (earlier) interpretation of the above results is preferred by Baker, based also on growth of stalagmites. In Sutherland, northwest Scotland, a spurt of four years of doubled annual luminescent growth banding of calcite in a stalagmite is datable to 1135 BC ±130.[6]

A rival, "low-chronology" interpretation of the eruption has been made by Andrew Dugmore: 2879 BP (929 BC ±34).[7] In 1999, Dugmore suggested a non-volcanic explanation for the Scottish results.[8] In 2000 skepticism concerning conclusions about connecting Hekla 3 and Hekla 4 (probably 2310 BC ±20) with paleoenvironmental events and archaeologically attested abandonment of settlement sites in northern Scotland was expressed by John P. Grattan and David D. Gilbertson.[9] Some Egyptologists have firmly dated the eruption to 1159 BC, and blamed it for famines under Ramesses III during the wider Bronze Age collapse.[10] Dugmore has rebutted this dating.[11] Other scholars have held off on this dispute, preferring the neutral and vague "3000 BP".[12]